由於隨著技術研發在不斷地提昇，但是當液晶面板的尺寸越來越大，其所使用的冷陰極螢光燈管（Cold Cathode Fluorescent Lamp, CCFL）的長度也越來越長，且使用的數目也越來越多，這時候的產品成本就成為企業能否延續其生命的主要因素。
  本篇論文中，我們以具零電壓全橋諧振式轉換器驅動電路具架構上簡單，體積小，不需另外加元件，仍然可以用寄生元件及諧振零電壓切換技術，降低開關元件切換的損失，不是讓寄生元件去減損電路的性能，利用相移控制達成，開關元件具零電壓(ZVS)切換特性，主要是用變壓器次級側洩漏電感，激磁電感，功率開關元件(MOSFET或IGBT)與其諧振電容產生諧振，以實現增加效率及可靠度。最後，藉著OZ Micr公司所設計的OZ9938控制IC，來完成使用於19”液晶顯示器，藉助外部光源達到顯示效果，光源則是以冷陰極螢光燈管為主。冷陰極螢光燈管的驅動電路泛稱為換流器，藉著換流器電路的硬體架構，讓讀者了解到，在諧振換流器為主來提供給液晶面板的背光模組(Backlight Unit, BLU)上的應用。

As technology developed rapidly, the size of the TFT-LCD panel grow larger and larger. Thus, the Cold Cathode Fluorescent Lamp (CCFL) contained became longer in
length, and more in number. A low product cost solution has become a crucial issue for lifetime enterprise.
  The purpose of this paper is to use the full-bridge phase-shift quasi-resonant converter that allows zero voltage turn-on of switches. While retaining the merits of simple circuit and small size, it uses the parasitic components to resonate. Therefore, additional resonant
components are not required. Moreover, the switching loss is reduced by the use of the zero voltage switching (ZVS) resonant technique. It uses phase-shift control to achieve the result. The transistor has the characteristic of zero voltage switching, using a transformer. A main combination of parasitic components, which includes the Metal Oxide Semiconductor Field Effect Transistor (MOSEFT) and second leakage inductance of the Isolation transformer,
produces a resonant action and reduces drain-source voltage prior to turn-on. Moreover, it achieved high efficiency and increased Mean Time Between failure (MTBF).
Finally, the OZ9938 controller IC manufactured by OZ Micr corp. is adopted in this thesis for use in 19” TFT-LCD with CCFLs from external light source, for the driver circuit of CCFL same as inverter, and introduced hardware aspects of the structure, so that readers understand quasi-resonant converter to the TFT-LCD of backlight unit application.

Table of Contents
Chinese Abstract…………………………………………………II
English Abstract ………………………………………………III
List of Figure……………………………………………VII 
List of Table………………………………………………………XII
List of Appendix……………………………………………………89
Chapter 1 Introduction
1.1 Motivation ……………………………………………………1
1.2 DTV Broadcasting System……………………………………3
    1.2.1 Integrated DTV……………………………………………4
    1.2.2 Industry Standards…………………………………4
1.3 TFT LCD TV systems block……………………………5
    1.3.1 Analog-Digital Converter, (ADC)…………………6
    1.3.2 Video Decoder…………………………………………6
    1.3.3 Tunner……………………………………………………7
    1.3.4 Transition Minimized Differential Signaling…7
    1.3.5 De-Interlacer…………………………………………7
    1.3.6 Scaler……………………………………………………7
    1.3.7 Audio Processor………………………………………8
    1.3.8 Micro Control Unit, (MCU)……………………………8
    1.3.9 Audio Amplifier…………………………………………8
    1.3.10 Low Voltage Differential Signaling………………8
    1.3.11 DC-DC Module…………………………………………9
1.4 Thin film transistor liquid crystal display module……9
    1.4.1 Introduction………………………………………………9
    1.4.2 Features………………………………………………9
 1.5 AC/DC module………………………………………………10
    1.5.1 DC/AC module………………………………………10
1.6 Summary…………………………………………………….10
Chapter 2 Background……………………………………………………12
2.1 Characteristics of Cold Cathode Fluorescent Lamps……12
    2.1.1 Fluorescent Lamp --- Physics……………12
    2.1.2 Characteristics of CCFL………………………13
    2.1.3 Inverter Requirements for Cold Cathode Fluorescent Lamps …………………18
2.2 Inverter Circuit Topology for CCFLs Driver…18
    2.2.1 Conventional Current-Fed Self-Oscillating Push- Pull Resonant Inverter…………………19
    2.2.2 Characteristics of various resonant tank……22
2.3 Analysis of Inverter Diagram for Multi-lamps system…35
Chapter 3 A Proposed Scheme of the Phase-Shift Full-Bridge Quasi-Resonant Inverter as Multiple CCFLs Driver………39
3.1 Operating Principle of the Phase-Shift Full-Bridge Quasi-Resonant Inverter………………………39
   3.1.1 Basic of Zero-Voltage Switching (ZVS) and Zero-Current Switching (ZCS)……………….41
   3.1.2 Zero-Voltage-Switching full bridge topology……44
   3.1.3  Inverter work steps…………………………46
   3.1.4 Inverter ZVS analysis…………………………48
3-2 Resonant Current Balance Topologies………………52
3-3 Comparison of balance diagram for CCFLs………55
3.4. Design and novel of balancing transformer for low voltage terminal of lamp……………………58
3.5 Striking Model of Open Lamp Protection System……61
Chapter 4 Design and Implementation of the Full-Bridge Quasi-resonant Inverter for Multiple CCFLs……………67
4.1 Introduce……………………………………………………67
   4.1.1 Control circuit………………………………………67
   4.1.2 OZ9938 Functional…………………………………….68
4.2 Multi-Lamp Design for LCD TV Application……………71
CHAPTER 5 Experimental results……………………73
5.1 Introduce………………………………………………73
5.2 Application Test……………………………74
5.3 The lamp strike voltage……………………………………75
5.4 Balance Inductance BT2 and Q1 (3904), D9 (BAV99) waveform during operation.78
5.5 Current Waveform of Lamp ………………………………80
5.6 Temperature Test………………………………83
5.7 Efficiency Test ……………………………83
Chapter 6 Conclusions and Future work……………………84
References………………………………………………86
Appendix. ……………………………………………………89
Patent number: M354270. ……………………………………89
List of Figure
Figure 1-1 DTV Broadcasting System………………4
Figure 1-2 Simplified functional block diagram……6
Figure 1-2-1 TFT – LCD Display………………10
Figure 2-1 A typical fluorescent lamp………… 13
Figure 2-2 A cold cathode fluorescent lamp……13
Figure 2-3 The characteristics of cold cathode fluorescent lamp ………………………………………14
Figure 2-4 Equivalent circuit of CCFL ……………………15
Figure 2-5 Ambient temperature vs. Brightness…………… 15
Figure 2-6 Lamp current vs. Brightness ………16
Figure 2-7 Lamp voltage vs. Lamp current…………………16
Figure 2-8 Spectral distribution…………………………17
Figure 2-9 Current-fed push-pull resonant inverter ……19
Figure 2-10 (a) Equivalent circuit of current-fed push-pull resonant inverter for CCFL; 
(b) Simplified equivalent circuit of (a)……… 20
Figure 2-11 Voltage and current waveforms of current-fed self-oscillating  push-pull resonant inverter………… 21
Figure 2-12 Block diagram of one-stage resonant inverter.22
Figure 2-13 Full-bridge converter topology ………23
Figure 2-14 Resonant topology (a) SRSL circuit topology; 
          (b) SRPL circuit topology; (c) SRPSL circuit topology………………………………… 24
Figure 2-15-1a. Magnitude response characteristics………………………………… 25
Figure 2-15-2a. Magnitude with variable cap response characteristics……………………………… 26
Figure 2-15-3a. Magnitude with variable loaded response characteristics ………………………………26
Figure 2-15-1b. Magnitude response characteristics …………………………………………………27
Figure 2-15-2b. Magnitude with variable cap response characteristics ……………………………….28
Figure 2-15-3b. Magnitude with variable loaded response characteristics……………………………28
Figure 2-15-1c. Magnitude response characteristics …………………………………………………...30
Figure 2-15-2c. Magnitude response ………31
Figure 2-15-3c.Magnitude with variable Cp response characteristics …………………31
Figure 2-15-4c. Magnitude with variable Cs response characteristics …………………32
Figure 2-15-5c. Magnitude with variable Cs, Cp response characteristics……………………………32
Figure 2-16  Frequency characteristics of resonant topology………………………………33
Figure 2-16-1  RLC resonant tanks of a low pass filter (a) Series resonant parallel-loaded (SRPL).(b) Relationship between Q of Lr to Cp and Rccfl at the resonant frequency. (c) Relationship between impedance Z(S) of Lr to 
Cp and Rccfl at the resonant frequency…………34 
Figure 2-17 1 to 1 of multiple lamps driving system with multiple control loops ………………36
Figure 2-18 A conventional multiple lamps driving system with single control loop …………………37
Figure 2-19 A conventional multiple lamps driving system with paralleled transformers.……………… 37
Figure 2-20 A multiple lamps driving system with lamp current balance control circuit at load end ………………38
Figure 3-1 Full-bridge phase-shift operation (a) Main circuit topology; (b) phase-shift operation waveforms…40
Figure 3-1-1, Comparison of resonant switching and hard switching ………………………………….41
Figure 3-2 Typical operation waveforms. (a) Four transistors with ZVS (b) Two transistors with ZVS and two with ZCS……………………………………………………… 42
Figure 3-3 Waveforms of gate signals for switches with dead time Td ……………………………………………… 42
Figure 3-3-1 Function description…………………………44
Figure 3-3-2: Full bridge circuit ……………45
Figure 3-3-3 OZ960 output waveforms ……………46
Figure 3-3-4: Stage 0 ..………………………………………46
Figure 3-3-5: Stage 1…………………………………………… 46
Figure 3-3-6: Stage 2……………………………………………47
Figure 3-3-7: Stage 3 ……………………………………………47
Figure 3-3-8: Stage 4 ……………………………………47
Figure 3-3-9: Stage 5. Stage 6……………………47. 48
Figure 3-3-10: Stage 7…….…………………………… 48
Figure 3-3-11: Stage 8 …………………………………..48
Figure 3-3-12  (VIN=7.0V)………………………… 49
Figure 3-3-13  (VIN=21.0V) …………………………….50
Figure 3-3-14  (Vin=7.0V)…………………………… 51
Figure 3-3-15  (Vin=21.0V)……………………………………… 51
Figure 3-4 Resonant current balance circuit scheme……… 52
Figure 3-5 Balance circuit of transformer scheme ……53
Figure 3-6 1 to1 for transformer and lamp ………55
Figure 3-7 Series of lamp a transformer ………56
Figure 3-8 Two lamps of a balance inductor …………56
Figure 3-9 Balancing transformer at the HV terminal……57
Figure 3- 10 Balancing transformer at the end terminal …………………………………57
Figure 3-11 Blancing transformer for low voltage terminal of lamp ………………………………58
Figure 3-11-1 RL1 and VS waveforms R1=R3=1.5M, R2=R4=330K (RL2 Open)…………………59
Figure 3-11-2 RL1 and VS waveforms R1=R3=330K, R2=R4=18K(RL2 Open)………………………59
Figure 3-11-3 RL1 and VS waveforms of RL2 Open after start on dimming ……………………………60
Figure 3-11-4 Operation RL1 and VS waveforms……………60
Figure 3-12-1 Open-lamp Protection circuit…………………61
Figure 3-12-2 Detector phase module……………………………64
Figure 3-12-3 Control module……………………………….64
Figure 4-1 Inverter Block of control………………………68
Figure 4-2 Function block diagram of OZ9938 ……………70
Figure 4-3.Balance current full-bridge circuit of driver 4 lamps by a transformer………………………72
Figure5-I : Normal Operation ……………………………………74
Figure 5-2 : Normal Operation: DRV1 - 4 Waveform…………74
Figure 5-3-1:Open Lamp1 …………………………75
Figure 5-3- 2 Open Lamp2…………………………… 75
Figure 5-3-3 Open Lamp 3……………………………76
Figure 5-3-4 Open Lamp 4 …………………………………………76
Figure 5-4: Open-lamp During Striking …………………77
Figure 5-5: Remove Panel During Normal Operation …………77
Figure 5-6: Drive Waveform of Primary Winding ……………78
Figure 5-7-1 Balance Inductance BT2……………………………78
Figure 5-7-2 Q1 (2N3904)……………………………………79
Figure 5-7-3 D9 (BAV99) waveform (Pin1 to Pin2)………79
Figure 5-7-3 D9 (BAV99) waveform (Pin2 to Pin3)………….80
Figure 5-8 Lamp CN2 = 6.73mA……………………………………80
Figure 5-9 Lamp CN3= 6.70mA …………………………81
Figure 5-10 Lamp CN4 = 6.67mA……………………………………81
Figure 5-11 Lamp CN5 = 6.72mA ………………………………82
Figure 5-12 PWM Dimming Control …………………82
Figure 5-13 ADJ=0.5V; CMP, DRV1, ISEN, output voltage waveform………………………………………………83
List of Table
Table3-1 Comparison of ZCS and ZVS ………………44 
Table 4-1 OZ9938 Functional Pin Description ……………69
Table 5-1 Operation configuration ……………………………73
Table 5-2  Instrument lists.............................73
Table 5-3 Current Waveform of Lamp ………………80
Table 5-4 Temperature Test: operating after 2 hours ……83

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